Swell packer

ABSTRACT

A swell packer includes a base tubular; a seal member encircling the base tubular, the seal member swelling radially to a seal equilibrium swell upon contact with a particular fluid; and a disc positioned about the base tubular substantially abutting an end of the seal member but not physically connected to the seal member in a manner that limits the equilibrium swell of the seal member, the disc swelling radially to a first equilibrium swell upon contact with a particular fluid.

TECHNICAL FIELD

The present invention relates in general to wellbore packers and morespecifically to packers that swell when exposed to a particular fluid orcondition in the wellbore.

BACKGROUND

It is often desired to utilize packers to form an annular seal inwellbores. Open-hole packers provide an annular seal between the earthensidewall of the wellbore and a tubular. Cased hole packers provide anannular seal between an outer tubular and an internal tubular.

Common types of packers include inflatable packers, mechanicalexpandable packers, and swell packers. Inflatable packers typicallycarry a bladder that may be pressurized to expand outwardly to form theannular seal. Mechanical expandable packers have a flexible materialexpanding against the outer casing or wall of the formation whencompressed in the axial direction of the well. Swell packers comprise asealing material that increases in volume and expands radially outwardwhen a particular fluid contacts the sealing material in the well. Forexample the sealing material may swell in response to exposure to ahydrocarbon fluid or to exposure to water in the well. The sealingmaterial may be constructed of a rubber compound or other suitableswellable material.

One drawback of swell packers is that the sealing material may extrude,due to differential pressure for example. Anti-extrusion, or anchoring,devices in the form of end-rings have been utilized as a means ofmediating this drawback. The end-rings typically include petals or thelike that expand outwardly by the force of the swelling seal material.While the end-rings may provide a benefit in some installations, casedhole installations it is believed that they may deter sealing in otherinstallations. For example, in open hole installations the ovality oreccentricity of the wellbore varies along its length. The non-uniformityin the cross-sectional shape and dimensions of the wellbore, means thatthe annular gap to be sealed may vary substantially from point to point.It also means that the dimension of the annular gap is often unknown.

SUMMARY

An example of an apparatus for supporting a radially swellable sealmember of a swell packer includes a radially swellable disc positionedat an end of the seal member. The disc may have a modulus of elasticitygreater than that of the seal member. The disc may have an internalstiffening element. A stiffening element may be operationally connectedto the disc opposite from the seal member. It may be that the disc isnot physically connected to the seal member, in a manner such that theconnection would limit the ability of the disc to expand to itsequilibrium swell.

An example of an anti-extrusion device positionable at an end of apacker seal member that radially swells when contacted by a particularfluid to form an annular seal in a wellbore includes a first disc forpositioning adjacent the seal member, the first disc expandable to afirst equilibrium swell upon contact with the particular fluid; and asecond disc positionable adjacent the first disc and opposite the sealmember, the second disc expandable to a second equilibrium swell uponcontact with the particular fluid, wherein the second equilibrium swellis less than the first equilibrium swell.

An example of a swell packer includes a base tubular; a seal memberencircling the base tubular, the seal member swelling radially to a sealequilibrium swell upon contact with a particular fluid; and a discpositioned about the base tubular substantially abutting an end of theseal member but not physically connected to the seal member in a mannerthat limits the equilibrium swell of the seal member, the disc swellingradially to a first equilibrium swell upon contact with a particularfluid.

The foregoing has outlined some of the features and technical advantagesof the present invention, in order that the detailed description of theinvention that follows may be better understood. Additional features andadvantages of the invention will be described hereinafter which form thesubject of the claims of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the present inventionwill be best understood with reference to the following detaileddescription of a specific embodiment of the invention, when read inconjunction with the accompanying drawings, wherein:

FIG. 1 is a conceptual illustration of an example of a swell packer andanti-extrusion device of the present invention;

FIG. 2 is a conceptual illustration of an example of swell packer of thepresent invention expanded and concentrically aligned in a wellbore;

FIG. 3 is a conceptual illustration of an example of a swell packer ofthe present invention expanded and eccentrically positioned in awellbore; and

FIG. 4 is an end view an example of a swell packer of the presentinvention activated in an open-hole wellbore.

DETAILED DESCRIPTION

Refer now to the drawings wherein depicted elements are not necessarilyshown to scale and wherein like or similar elements are designated bythe same reference numeral through the several views.

FIG. 1 is a conceptual illustration of an example of a swell packer ofthe present invention, generally denoted by the numeral 10. Swell packer10 includes a base tubular 12, swellable seal member 14, and ananti-extrusion device generally denoted by the numeral 16. Swell packer10 has a longitudinal axis 18 shown by the dashed line.

Swell packer 10 is shown disposed in a wellbore 20 having a sidewall 22.Open-hole refers to sidewall 22 being formed by the surrounding earthenformation. Cased hole refers to the sidewall 22 being formed by atubular. The tubular may be a casing, liner, tubing, production string,screen or in general any other tubular in which packer 10 is positioned.

Seal member 14 has opposing ends 24, 26 and encircles base tubular 12.Seal member 14 may be may be connected to base tubular 12 in variousmanners. Seal member 14 is formed of a material that swells when exposedto a particular fluid or condition in wellbore 20. For example, sealmember 14 could swell in volume in response to a hydrocarbon, water, orother activating fluid or chemical. Seal material 14 may be of a rubbercompound or other material. Seal member 14 may be constructed as aunitary member or in layers. To form an annular seal, seal member 14must expand radially the distance of annular gap 34, which is thedistance between the outer surface of seal member 14 and sidewall 22.

Anti-extrusion device 16 may be positioned about base tubular 12 at oneor both of ends 24, 26 of seal member 14. Anti-extrusion device 16includes one or more discs 28. Discs 28 are formed of a swellablematerial. Anti-extrusion device 16 is now described with reference tothe left end of seal member 14, referred to herein as end 24.Anti-extrusion device 16 includes multiple discs identified as 28 a, 28b, 28 c, 28 d, etc. from the end 24 of seal member 14 outward. Although,four discs are illustrated in the Figures, device 16 may include more orfewer discs 28.

Adjacent discs 28 are in functional connection with one another so as tocooperatively provide support to seal member 14 against extrusionwithout limiting the radial expansion of seal member 14. Adjacent discs28 may physically abut one another or may be spaced apart by one or moreelements. Anti-extrusion device 16 may include various non-swellableelements such as reinforcement members, components, and the like.

Each disc 28 may be constructed of a material having a differentswellability and modulus of elasticity than its adjacent disc.“Swellability” is utilized herein to denote the ability to increase involume and extend radially outward from base tubular 12. In theillustrated example, discs 28 decrease in swellability as they moveoutward from an end of seal member 14. Thus, disc 28 a has a greaterswellability than disc 28 b which has a greater swellability than disc28 c, and so forth. As the swellability decreases, the modulus ofelasticity, or Young's Modulus, increases. Thus, the discs become morerigid or stiffer as they move outward from the end of seal member 14.

Discs 28 may be constructed of materials such as, but not limited to,swellable rubber compounds and non-elastomeric plastics. Examplesinclude Ryton/elastomer blender, Xtel XE3200 polyphenylene sulfide alloywith 100 percent elongation at break and 450 psi tensile strength,PVDF/Viton blends, and thermoplastic elastomers.

Refer now to FIG. 2, wherein swell packer 10 is illustrated in theexpanded position. In this example, swell packer 10 is concentricallyaligned within wellbore 20. The longitudinal axis 36 (FIG. 3) of thisportion of wellbore 20 corresponds to longitudinal axis 18 of packer 10and is therefore not visible in this view. FIG. 2 illustrates aninstallation that is common to cased holes.

Upon contact with a selected fluid, seal member 14 and discs 28 ofanti-extrusion device 16 swell and expand radially outward from basetubular 12 to their respective equilibrium swells or until contained bysidewall 22. Discs 28 b, 28 c, and 28 d have each reached theirrespective equilibrium swell in FIG. 2. Disc 28 a may have reached itsequilibrium swell or it contacted sidewall 22 prior to reachingequilibrium.

Disc 28 a, being the disc adjacent to the end of seal member 14 has aswellability similar to the swellability of seal member 14. In someexamples, disc 28 a will have a swellability less that that of sealmember 14 and thus have a higher modulus than seal member 14. Disc 28 ais not physically connected to seal member 14 in a manner that willlimit seal member 14 from obtaining its equilibrium swell. The rigidityand the swellability of disc 28 a, aides in preventing or limiting theextrusion of seal member 14, while not interfering with the ability ofseal member 14 to contact and form a seal against sidewall 22. Eachsubsequent disc (28 b, 28 c, etc.) out from the end of seal member 14decreases in swellability and increases in stiffness (higher modulus ofelasticity), thus providing additional support against extrusion of sealmember 14.

Anti-extrusion device 16 may include one or more elements to provideadditional rigidity. For example, device 16 may include an external orfirst stiffening element 30, such as an expandable end-ring that isspaced apart from seal member 14 and abutting a disc 28. Anti-extrusiondevice 16 may include disc 28 a abutting an end of seal member 14 and afirst stiffening element 30, such as an end-ring, that is operationallyconnected to the end of disc 28 a opposite of seal member 14. Stiffeningelement 30 may provide the support to disc 28 a necessary to prevent orlimit the extrusion of seal member 14 without materially limiting theability of seal member 14 to expand radially. In one example, disc 28 amay have a swellability and modulus of elasticity that is the same orsubstantially the same as seal member 14.

Device 16 may include internal or second stiffening elements 32.Examples of second stiffening elements 32 include without limitation,Kevlar, glass, and carbon incorporated into discs 28 for example aschopped fibers, fiber mats, and long fibers.

Refer now to FIGS. 3 and 4 illustrating swell packer 10 activated in anopen-hole wellbore 20. Swell packer 10 is shown eccentrically positionedin wellbore 20, indicated by the misalignment of longitudinal axis 18 ofbase tubular 12 and longitudinal axis 36 of wellbore 20 (FIG. 3).

As is common in open-hole wellbores, the cross-sectional dimensions ofwellbore 20 is non-uniform along its length. The unpredictability of thewellbore dimensions at the desired seal location creates difficulties inobtaining an effective seal. One difficulty is presented by theinability to determine the annular gap at the desired point of sealing.The inability to accurately identify the annular gap at the point of theseal may result in the mis-sizing of the traditional anti-extrusiondevices, in particular the end-ring type devices. The mis-sizing of thetraditional anti-extrusion devices may not only fail to operate asdesired but may in fact prevent the seal member from sealing against thesidewall. For example, if an tradition end-ring is selected for anannular gap less than the actual annular gap to be sealed, thetraditional end-ring may prevent the sealing element from expandingsufficiently to achieve the desired seal.

Anti-extrusion device 16 does not grip seal member 14 in a manner thatwill limit the radial expansion of seal member 14. As illustrated inFIG. 4, seal member 14 is free to expand radially from base tubular 12to seal against the contour of sidewall 22. Disc 28 a swells radially toan extent to aide against extrusion of seal member 14 without limitingthe radial expansion of seal member 14. As can be seen in the end-viewof FIG. 4, disc 28 a may expands to sidewall 22 or may reach itsequilibrium swell before reaching sidewall 22 without limiting theradial expansion of seal member 14.

From the foregoing detailed description of specific embodiments of theinvention, it should be apparent that swell packers and anti-extrusiondevices for swell packers that are novel have been disclosed. Althoughspecific embodiments of the invention have been disclosed herein in somedetail, this has been done solely for the purposes of describing variousfeatures and aspects of the invention, and is not intended to belimiting with respect to the scope of the invention. It is contemplatedthat various substitutions, alterations, and/or modifications, includingbut not limited to those implementation variations which may have beensuggested herein, may be made to the disclosed embodiments withoutdeparting from the spirit and scope of the invention as defined by theappended claims which follow.

1. An apparatus for supporting a radially swellable seal member of aswell packer, the apparatus comprising a radially swellable discpositioned at an end of the seal member.
 2. The apparatus of claim 1,wherein the disc has a modulus of elasticity greater than that of theseal member.
 3. The apparatus of claim 2, wherein the disc includes aninternal stiffening element.
 4. The apparatus of claim 2, furtherincluding a stiffening element operationally connected to the discopposite from the seal member.
 5. The apparatus of claim 2, wherein thedisc is not physically connected to the seal member.
 6. The apparatus ofclaim 3, further including a stiffening element operationally connectedto the disc opposite from the seal member.
 7. The apparatus of claim 6,wherein the disc is not physically connected to the seal member.
 8. Theapparatus of claim 1, wherein the disc is radially less swellable thanthe seal member.
 9. The apparatus of claim 1, further including astiffening element.
 10. The apparatus of claim 9, wherein the stiffeningelement is operationally connected to the exterior of the disc oppositefrom the seal member
 11. The apparatus of claim 1, further including astiffening element operationally connected to the exterior of the discopposite from the seal member.
 12. The apparatus of claim 11, whereinthe stiffening element is an end-ring.
 13. The apparatus of claim 11,wherein the disc is not physically connected to the seal member.
 14. Ananti-extrusion device positionable at an end of a packer seal memberthat radially swells when contacted by a particular fluid to form anannular seal in a wellbore, the device comprising: a first disc forpositioning adjacent the seal member, the first disc expandable to afirst equilibrium swell upon contact with the particular fluid; and asecond disc positionable adjacent the first disc and opposite the sealmember, the second disc expandable to a second equilibrium swell uponcontact with the particular fluid, wherein the second equilibrium swellis less than the first equilibrium swell.
 15. The device of claim 14,further including a stiffening element.
 16. A swell packer comprising: abase tubular; a seal member encircling the base tubular, the seal memberswelling radially to a seal equilibrium swell upon contact with aparticular fluid; and a disc positioned about the base tubularsubstantially abutting an end of the seal member but not physicallyconnected to the seal member in a manner that limits the equilibriumswell of the seal member, the disc swelling radially to a firstequilibrium swell upon contact with a particular fluid.
 17. The swellpacker of claim 16, further including a stiffening element operationallyconnected to the disc opposite the seal member.
 18. The swell packer ofclaim 16, wherein the first swell equilibrium is less than the sealswell equilibrium, and the disc is more rigid at the first swellequilibrium than the seal member is at the seal swell equilibrium. 19.The swell packer of claim 18, further including a second disc positionedabout the base tubular adjacent the disc opposite the seal member, thesecond disc swelling radially to a second equilibrium swell upon contactwith a particular fluid, wherein the second equilibrium swell is lessthan the first equilibrium swell.
 20. The swell packer of claim 19,further including an external stiffening element positioned between thedisc and the second disc.